Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756200AbbEUUXu (ORCPT ); Thu, 21 May 2015 16:23:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43469 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755792AbbEUUXr (ORCPT ); Thu, 21 May 2015 16:23:47 -0400 From: jglisse@redhat.com To: akpm@linux-foundation.org Cc: , linux-mm@kvack.org, Linus Torvalds , , Mel Gorman , "H. Peter Anvin" , Peter Zijlstra , Andrea Arcangeli , Johannes Weiner , Larry Woodman , Rik van Riel , Dave Airlie , Brendan Conoboy , Joe Donohue , Duncan Poole , Sherry Cheung , Subhash Gutti , John Hubbard , Mark Hairgrove , Lucien Dunning , Cameron Buschardt , Arvind Gopalakrishnan , Haggai Eran , Shachar Raindel , Liran Liss , Roland Dreier , Ben Sander , Greg Stoner , John Bridgman , Michael Mantor , Paul Blinzer , Laurent Morichetti , Alexander Deucher , Oded Gabbay , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= Subject: [PATCH 26/36] HMM: fork copy migrated memory into system memory for child process. Date: Thu, 21 May 2015 16:23:02 -0400 Message-Id: <1432239792-5002-7-git-send-email-jglisse@redhat.com> In-Reply-To: <1432239792-5002-1-git-send-email-jglisse@redhat.com> References: <1432236705-4209-1-git-send-email-j.glisse@gmail.com> <1432239792-5002-1-git-send-email-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2001 Lines: 76 From: Jérôme Glisse When forking if process being fork had any memory migrated to some device memory, we need to make a system copy for the child process. Latter patches can revisit this and use the same COW semantic for device memory. Signed-off-by: Jérôme Glisse --- mm/hmm.c | 38 +++++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) diff --git a/mm/hmm.c b/mm/hmm.c index 1208f64..143c6ab 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -487,7 +487,37 @@ int hmm_mm_fork(struct mm_struct *src_mm, unsigned long start, unsigned long end) { - return -ENOMEM; + unsigned long npages = (end - start) >> PAGE_SHIFT; + struct hmm_event event; + dma_addr_t *dst; + struct hmm *hmm; + pte_t *new_pte; + int ret; + + hmm = hmm_ref(src_mm->hmm); + if (!hmm) + return -EINVAL; + + + dst = kzalloc(npages * sizeof(*dst), GFP_KERNEL); + if (!dst) { + hmm_unref(hmm); + return -ENOMEM; + } + new_pte = kzalloc(npages * sizeof(*new_pte), GFP_KERNEL); + if (!new_pte) { + kfree(dst); + hmm_unref(hmm); + return -ENOMEM; + } + + hmm_event_init(&event, hmm, start, end, HMM_FORK); + ret = hmm_migrate_back(hmm, &event, dst_mm, dst_vma, new_pte, + dst, start, end); + hmm_unref(hmm); + kfree(new_pte); + kfree(dst); + return ret; } EXPORT_SYMBOL(hmm_mm_fork); @@ -662,6 +692,12 @@ static void hmm_mirror_update_pte(struct hmm_mirror *mirror, } if (hmm_pte_test_valid_dev(hmm_pte)) { + /* + * On fork device memory is duplicated so no need to write + * protect it. + */ + if (event->etype == HMM_FORK) + return; *hmm_pte &= event->pte_mask; if (!hmm_pte_test_valid_dev(hmm_pte)) hmm_pt_iter_directory_unref(iter, mirror->pt.llevel); -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/